1. Field of the Invention
The present invention relates to a copying machine which forms an image by directing light reflected from a document or transmitted through a slidefilm onto a photosensitive sheet.
2. Description of the Prior Art
In recent years, there have been developed copying machines capable of copying images formed in slidefilms. Two methods for copying from slidefilms are known. In one method, the entire surface of a stationary photosensitive material is exposed to light transmitted through a slidefilm. In the other method, a slide projector is mounted on the document table of a document scanning type copying machine, and the slide projector is used to project light transmitted through a slidefilm into a Fresnel lens, the projected light being directed onto a photosensitive material by means of a scanning type optical device to subject the photosensitive material to slit exposure for forming an image thereon.
However, the former method has the problem that the size of the apparatus tends to increase. On the other hand, with the latter method, the loss of optical brilliancy is great and, since the slide projector is mounted on the document table, there is a possibility of scratching, breaking or causing other damage to the document table. Therefore, it is not a practical method. In view of such problems, there has been proposed a method in which a slide projector is detachably mounted in a copying machine and light projected through a slidefilm by the slide projector is transmitted directly onto a photosensitive material to expose the photosensitive material for forming an image thereon.
As an example, in a copying machine which forms an image by superimposing and pressing a photosensitive sheet coated with microcapsules containing photohardening materials and coloring dyes onto an image receiving sheet coated with developer that develops colors by reacting with the coloring dyes, a slide projector is detachably mounted in such a way that the light transmitted through a slidefilm is projected directly onto the photosensitive sheet, and the light path of the slide projector is made to coincide with the light path of the reflected light from the document on the document table just before reaching the photosensitive sheet. There is also provided, at a position where the light path of the reflected light from the document meets the light path of the light projected by the slide projector, a movable mirror which selects either the reflected light from the document or the slide projector light and directs the selected light to the photosensitive sheet. The movable mirror is movable between a position where the light reflected from the document and passed through a lens is reflected for projection onto the photosensitive sheet and a position where the light transmitted through the slidefilm and projected by the slide projector is allowed to be projected directly onto the photosensitive sheet.
Since the slide projector is mounted so as to be positioned on an extension produced from a portion of the light path of the document reflected light that is directed by the movable mirror to the exposure position on the photosensitive sheet, the mounting position of the slide projector is approximately at the same height as that of the optical device of the copying machine. When the slide projector is mounted in the copying machine, the light path extending from the light source of the slide projector, passing through the slidefilm, and reaching the photosensitive sheet loaded in the copying machine is formed by the selective movement of the movable mirror. The slidefilm mounted in a movable slidefilm holder is moved to a prescribed position, and the light from the light source is projected through the slidefilm, a slit, and a lens onto the exposure position of the photosensitive sheet for slit exposure of the photosensitive sheet.
In an image forming apparatus using a photosensitive sheet and the image receiving sheet, since the sensitivity of the photosensitive sheet is lower than that of the photoconductor drum used in a conventional copying machine, a greater amount of exposure is needed. As a result, the temperature of the light source increases considerably, which in turn causes the temperature of the document table and the optical device to increase considerably. To prevent such heating, cooling of the light source is provided from the vicinity thereof along with cooling by outside air introduced from one side of the copying machine and circulated through to the other side thereof.
However, since the slide projector is mounted in one side of the copying machine and approximately at the same height as that of the optical device, as described previously, the air circulation path of an optical device cooling fan, which is usually mounted on the side of the copying machine nearer to the scanning start position side of the optical device, becomes blocked by the slide projector mounted in position, thus preventing smooth circulation of cooling air through the copying machine and decreasing the cooling efficiency in the area of the optical device and the document table.